For the purposes of this specification, the term “diffuser” is used to designate those devices which, in air conditioning systems, are employed for the purpose of regulating flow of air, which may be heated air or cooled air, from air conditioning ducting into a room.
Various conditions occur in an air conditioned room depending on whether the outside temperature is above or below that at which the room is to be maintained, i.e. above or below the so-called “set point”. Thus in cooling or “summer” conditions, the diffuser should control the rate at which cooled air is fed to a room and in heating or “winter” conditions, the diffuser should similarly control the rate at which heated air is fed to the room.
It is often desirable for an air conditioning system, or more particularly for a diffuser, to have different set points for cooling and heating conditions. The reasons may partly be because of personal preferences of occupants of the rooms, but typically, people dress according to the ambient temperatures and their bodies adjust to the ambient temperature, so that they can tolerate some degree of cold when it is cold outside and can tolerate some degree of heat if it is hot outside. In fact, occupants of air conditioned spaces where temperatures are kept perfectly constant usually experience these spaces as too hot when it is cold outside and/or too cold when it is hot outside. Experience has shown that most occupants of air conditioned spaces are most comfortable if the set point during cooling (summer) conditions is about one to two degrees Celsius higher than the set point for heating (winter conditions). This temperature difference between cooling and heating set points will be referred to in this specification as the “offset”.
In addition to the advantages that such an offset has for comfort, it also saves considerable amounts of energy in avoiding unnecessary cooling and/or heating. Further, apart from the savings in energy costs, the lower energy consumption is also important in striving for the provision of buildings that are more environmentally friendly, or so-called “green buildings”.
In the specification of South African Patent Application No. 2005/06813, the entire contents of which is included herein by reference, (corresponding to U.S. Pat. No. 7,189,159 and Australian Patent Application No. 2005205768) diffusers are disclosed in which the set points in respect of cooling and heating conditions can be adjusted independently of each other. In the diffusers disclosed in each of these patent specifications, there is an adjustment element that can be rotated to adjust the set point for heating conditions and similarly, there is a substantially identical adjustment element that can be rotated to adjust the set point for cooling conditions.
The independent adjustment of set points for heating conditions and cooling conditions make these systems prone to loosing its offset. What typically happens is that a user who prefers a cooler environment feels hot during cooling conditions (summer) and adjusts the cooling set point downwardly without adjusting the heating set point, thus reducing the offset. When the diffuser is then operated in heating conditions (winter), the original heating set point is maintained, even though it would have been more comfortable for the user and less heating energy may have been used if the heating set point were also lowered, i.e. the offset were maintained. Similarly, energy wastage and/or discomfort can occur in the exact opposite scenario, if the offset is reduced by raising the heating set point without raising the cooling set point and energy is subsequently wasted in excessive cooling.
The desirability of maintaining an offset and/or the quantum of the offset can vary depending on the particular use of the diffuser. An increase in the offset may for instance improve energy efficiency, but can cause some discomfort and a balance may need to be struck between these two considerations, which suits the particular case. It may be that in spaces that are less prone to temperature variations, the cost of heating and/or cooling is minimal and only a small or no offset is desirable. Accordingly, some users may require the capability to adjust the offset.
The present invention seeks to provide an improved diffuser that allows convenient simultaneous adjustment of its set points for heating and cooling conditions, while maintaining an offset and that allows its offset to be adjusted.